Telephone-exchange system



Sept. 28, 1926.

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- v 1,601,052 S. B. WILLIAMS TELEPHONE EXCHANGE SYSTEM 12 Sheets-Sheet 12 Filed March 22 2 flare/fianjamue/ 5 IIW/fams Patented Sept. 28, 1926.

UNITED STATES PATENT OFFICE.

SAMUEL B. WILLIAMS,

COMPANY, INCORPORAT Application filed March 22, 1924, Serial No.

This invention relates to telephone exchange systems and more particularly to systems employinw automatic switching apparatus for establishing connections.

An object of the invention is to intercept calls which are directed to certain lines or stations before the switches have fully operated to establish a such calls in a different connection and to route direction.

A feature of the invention relates to the provision, in a system employing switch con? trolling markers common to the selector switches and translators associable withthe markers and switches, of means in the translators serving to intercept calls directed to certain lines and to cause the calls to be routed to an operator.

Another feature relates to a translator,

common to the subscribers lines for controlling the switches to make connection to such lines, wherein the lines are so represented that calls on one of said to one or more stations lines may be intercepted and directed to an operator. Still another feature relates to the provision, in a system in which the called lines are divided each group governing in groups with a translator for the connector switches which make connection to said lines, of means in the translator whereby each line of that group is represented and whereby calls to an line may be intercepted independent of the connector switch having access to said line.

Another object divide the trunks switch into groups ciating the marker for testing of the invention is to incoming to a selector and to provide for assopiirposes with the particular group which contains the trunk over which a connection has been extended.

Another object of the inventionis an improved method of giving the calling party a busy notification.

According to this latter object, a busy tone apparatus is associated with one of the selective switches and appearing in the contacts thereof, together with means for partially releasing the attempted connection to a called line when such line is busy and for reestablishing the connection through 01 BROOKLYN, NEW YORK,

. necto'r ASSIGNOR TO WESTERN ELECTRIC ED, 01: NEW YORR, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHAN GE SYSTEM.

701,006. Renewed April 5, 1926.

said switch to seize the busy tone equipment. Referring to the drawing, Figs. 1 to 12 nclusive when taken in the order illustrated in Fig. 13 disclose a portion of a telephone exchange system embodying the features of this invention.

Fig. 1 shows diagrammatically a line switch 111 which calling lines appear, a district selector switch, a sender selector switch and a portion of one of the register senders. Fig. 2 shows an incomin selector switch in which terminate trunks eading from the district selector shown in Fig. 1.

Fig. 3 shows a portion of one of the final or connector sw tches in which terminate the called subscribers lines.

4, 5 and 6 illustrate the registers of the sender partially shown in Fig. 1.

Fig. 7 shows a sender connector for connecting the register senders to the markers.

Figs. 8 and 9 illustrate one of the common markers, the function of which is to control the incoming and final switches.

Fig. 10 shows an incoming frame confor connecting the markers to the frames of the incoming selectors.

Fig. 11 shows a translator connector, the purpose of which is to connect any of the markers with any of a number of final translators.

Fig. 12 illustrates one of the final translators, the function of which is to cooperate with the marker in the control of the final switches.

General description of the circuits and apparatus.

200 in turn have access to groups of trunks which lead to different groups of final connector switches 300 which in turn have access to the called subscribers lines.

The line switches 101, sender selectors 103, district selectors 109, incoming switches 200 and connector switches 300 are of the coordinate type such as generally shown and described in the copending application of C. L. Goodruin and J. N. Reynolds, Serial No. 486,442, filed July 21, 1921, Patent No. 1,515,735, ranted Nov. 18, 1924.

Inasinuc as the present invention 18 concerned particularly with the operation and control of the incoming and final switches 200 and 300, it has not been considered necessary to go into the details of the operation of the line switch, the district selector, the sender selector or the subscribers register sender. The operation of these; switches and of the register sender may be substantially the same as that fully described in the patent to S. B. Williams, No. 1,517,331, granted Dec. 2, 1924. lVherever detailed operations are referred to hereinafter and are not fully illustrated, reference ismade to said application for an understanding thereof.

The total number of incoming selector switches 200 may be divided in a number of groups each of which receives trunks from the district selector switches 109. For each of these groups there may be provided a frame connector 1000 which serves to connect any of the incoming markers to the incoming frames of this particular group. In order that the marker may select and operate the roper frame connector it receives certain infbrination from the register sender for this purpose. The trunks 110 which have access to a particular group of incoming frames, may be segregated on certain vertical rows of the district selectors 109. The same is true of trunks 110 leading to other groups of incoming frames. Therefore, when the marker is connected to the outgoing trunk group, at the time switch 109 is operating a circuit may be closed from the contact of magnet 116 through the marker 115 to operate relay 108 in the sender. An indication is thus given to the sender relative to the particular group of incoming selector switches that is to be involved in establishing the connection. During the time the sender is associated with the incoming marker shown in Figs. 8 and 9 this information is transferred to the latter mechanism.

The subscribers lines considered as called lines are divided into a suitable number of groups. If it is assumed that the exchange comprises 10,000 lines, it may be convenient to divide these into five groups of 2,000 lines each. For each group of 2,000 lines a suitable number of connector switches 300 are provided for making connection therewith. Furthermore, each group of 2,000 lines is provided with a final translator 1200 which is common to all of the connector switches of the group and serves to selcctivel y opcrate the same. The translator 1200 is made up of forty multi-contact relays 1208, 1212, 1213 and so forth. Each of these relays has contacts individually representing litty different subscribers lines. "he grid wires with which these relays make contact are divided into ten different sections 121-1, 1215 and so forth, each section representing five different lines for each relay. Since there are forty relays in the translator, twenty of these represent the lines in the even thousand and the other twenty represent the lines in the odd thousand. Two relays in each thousand represents the lines of a given 100 therein, both in the even and odd thousands.

There being ten hundreds in each thousand, ten relays 1211, 1216 and so forth are provided. Accordingly, each relay represents a given hundred in both the even and odd thousand. The relays 1217 and 121s determine the value of the units digit of the wanted line. For instance, if the units digit is lessthan five, one of these relays 0P0! ates, whereas, if the units digit is greater than four, the other relay operates. 7

The value-of the tens digit is determined by one of tens relays 1209, 1210 and so forth.

Thus with the proper hundreds relay operated, with the proper one of the relays 1217 and 1218 operated and by knowing Whether the thousand is even or odd, the particular one of the inulti-contact relays of the translator is selected which represents the fifty lines in the proper thousand. in the proper hundred, having units digit: greater than four or less than five, as the case may be. By thereupon operating the proper one of the tens relays 1209, 1210 and so forth, the selection is reduced to the particular five lines including the wanted subscrihers line.

The connector switches 300 comprises five sets of horizontal links 311, 312 and so forth. The subscribers lines appear in the vertical rows of contacts 303, 301 and so forth, each line appearing before all of the horizontal links in the section. Thus. the vertical row of contacts 303 includes five different lines and two of these vertical rows together make up the tens lines, each having a different one of the ten units digits. It will be noted that this arrangement corresponds wirh the representation of the subscribers lines in the translator 1200.

The trunks outgoing from the incoming selector switches 200 appear in vertical rows 203, 204 and so forth, each group of trunks 832 in order to the particular one of the five horizontal sections the connector switchin which appears the may be operated in combinations such that called subscribers line.

Referring again to the incoming selectors, these switches are divided into several horizontal sections 832,833, etc. Each section comprises a separate group of horizontal links, and the incoming trunks are multipled to appear before the horizontal links of only one section. For instance, the section 832'includes the links 205 and 206, and a group of incoming trunks including the trunk 110 appears only before the horizontal links of this section.

When the marker is associated with the incoming selector switch, as will be hereinafter described in detail, arrangement is made whereby such marker will be connected only to the horizontal links of the section or oup in which appears the incoming trunk over which the connection has been extended. The reason for this is obvious. If, for instance, the incoming connection has been extended over trunk 110, it is desirable that the marker be associated with the section to test the links 205, 206, etc., inasmuch as these are the only links which can ,be involved in the further extension of the incoming trunk.

The selective association of the marker with the proper one of the different groups of horizontal links and the incoming switch is accomplishedby means of the incoming 'frame connector 1000. This frame connector is made up of a number of multi-contact relays 1001, 1029, etc. Each of these relays in addition to identifying a particular incoming frame 200, also identifies a given section of horizontal links or thecorresponding group of trunks incoming to said frame; The relay 1001 represents the frame 200 and also represents the group of incoming trunks appearing in the section 832 of horizontal links. Therefore, whenever a connection is extended over one of the trunks 110 appearing in the section 832, the relay 1001 is operated to connect the marker'testing leads to he test conductors of the horizontal link circuits 205, 206, etc.

The multi-contact relay 1029 represents transmitted to the sender which serves to connect the.

the same frame 200, but this relay is only operated whenever a connection is extended over one of the incoming trunks which appears inthe horizontal links of the section 833. In a similar manner, other groups of horizontal links and other identifying relays in the frame connector 1000 may be provided. f

In order to intercept calls made to any particular line, there is provided a set of relays 1203. By connecting these relays arbitrarily to the necessary points on the distributing frames 1220 and 1221, the proper relay or combination of relays may be operated whenever a call is directed to the line in question.

In the case of party lines, these relays Detailed description of the operation.

Extension of a connection to a, party line-It will be assumed that the subscriber of line 100- wishes to hold a conversation with the subscriber at station J on the party line 318, and that the designation of the desired station is COR 2234PJ. Accordingly, the calling subscriber initiates the call, whereupon the line switch 101 operates. to

extend the line to an idle trunk 102 leading to the district selector 109 and whereupon the sender selector switch 103 operates automatically and extends the subscribers line to an idle register sender 107.

The calling subscriber now transmits impulses to the sender representing the office code designation COR. These impulses are received in the sender and are recorded on the first three registers 600, 601, and 602 of the register mechanism. The first series of impulses representing thelett-er C is recorded on the. register 600 by placing ground potential on the proper conductors of the group 111 leading from the sender 107. The conductors 111 are extended to the relays of the register 600 by means of the cut-in relay 603.

The second series of impulses representing the letter 0 cause the operation of the register relays-601, the cut-in relay 604 having operated by means of a circuit completed in the sender and extending through the front contact of relay 606.

After this, relay 607 operates, followed by the operation of relay 605, and the third series of impulses representing the letter R is recorded on the register 602.

In a similar manner, the four numerical digits and the stations digit J (the latter being represented by five impulses) are and recorded on the registers 500, 502, 400, 401 and 402. It will be assumed that the thousands digit 2 causes the operation of the register relay 503 of the thousands register 500; that the hundreds digit 2 causes the operation of relay 508; that the tens digit 3 causes the operation of relays 403 and 404; that the units digit 4 causes the operation of relav 408; and that. the stations digit J causes the operation of relay 409. Relay 503 in operating, operates the relay 504 in a circuit from battery through the winding of relay 504, inner right contact of relay 503, outer right back contact of relay 505. left contact of relay 503, thence over the operating conductor 506, to ground. It will be understood, of course, that the register relays having operated, may be locked in any suitable manner.

The oiiice registers shown in Fig. 6 upon receiving the ottice code, are connected to an outgoing marker 115 which governs the operation of the district selector switch 109 to extend the subscribers line over an idle trunk 110 leading to the proper group of incoming selector switches 200.

\Vhen all of the digits have finally been received and recorded in the register sender, the sender causes ground potential to be placed upon conductor 112, which operates the relay 701 of the sender connector 700. The relay 701 locks in a circuit from battery, through the winding of relay 7 02, upper winding of relay 701, to ground over conductor 112. Relay 702 also operates and prevents the subsequent operation of another relay similar to relay 701 in case a second sender attempts connection to a marker. The multi-contact relay 703 is now operated in a circuit from battery, through its winding. lower contact of relay 701, outer back contact of relay,704 to ground atthe contact of relay 702. Relay 703 looks through its contact to ground at the left contact of relay 702.

Relay 702 operates the relay 7 06 which relates to the first idle marker (it being assumed that the marker represented by relay 709 is busy at the time). The circuit for relay 706 may be traced from ground, through the inner right contact of relay 702, back contact of relay 704, front contact of relay 710, lower contact of relay 709, back contact of relay 705, lower winding of relay 706, to battery through the contact of relay 708. Relay 706 operates and locks in a circuit from batter through the winding of relay 708, contact and upper winding of relay 7 06, conductor 711, to round at the contact of relay 702. Relay (08 also operates in this circuit. Relay 706 operates the relay 704 in a circuit from battery, through the winding of the latter rela upper contact of relay 706, to ground at t e contact of relay 708. The multi-contact relay 707 is next operated to extend the various leads from the sender to the idle marker. The circuit for rela 7 07 may be traced from battery, through the winding thereof, contact of relay 706, to ground at the contact of relay 708. Relay 705 also operates in parallel with relay 707.

As soon as the sender is connected to the marker, the holding relay 900 is operated in a circuit from battery, through the winding thereof, conductor 901, through the connector 700, conductor 902, to ground in the sender. Relay 900 locks in a circuit through its winding and contact, right back contact of rela Y 903, to ground at the inner left contact 0t slow relay 904.

The record of the thousands, hundreds, tens, units and stations digits and of the particular group of incoming switches involved, is now transferred from the sender to the marker. First considering the record of the group of incoming selectors to which the trunk 110 extends, it will be noted that this trunk appears in the district selector 109, in the row controlled by the vertical magnets 116. Therefore, when the magnet 116 operates during the association of the marker 115 with the selector switch, it operates the relay 108 in the sender. lVith relay 108 operated and with the sender connected to the marker as explained, a circuit is established for operating the frame test relay 806 and may be traced from battery, through the winding of said relay, conductor 807, thence over conductor 712, to ground at the contact of relay 108. The function of relay 806 will be described hereinafter. 1

Since the relay 504 of the register 501 is operated in the sender, relay 808 is energized in circuit from battery, through the winding of said relay, conductor 812, thence over conductor 713, front contact of relay 504 and returning over conductor '510, thence to conductor 714, inner right contact of relay 905, conductor 909, outer left contact of relay 910, right back contact of relay 911, inner right contact of relay 912, conductor 913, to ground at the contact of relay 900. Since the remaining relays 511, 512 and 513 of the register 501 remain deenergized temporary circuits are closed for operating relays 840, 841 and 842, which may be traced through the windings of these latter relays, thence through the sender connector 700, over conductors 515, 516 and 517. through the back contacts of relays 511, 512 and 513, respectively, thence over conductor 518, conductor 715, back contact of relay 809, normal contact of relay 810, conductor 811, thence to ground over conductor 714, as previously traced.

lVith the hundreds register relay 508 opperated a circuit is closed for relay 813 traceable from battery through the winding of said relay, conductor 824, thence to conductor 716, front contact of relay 508, thence to of all the register re memos the grounded conductor 510. Since the remaining relays of register 502 are deenergized, relays 812, 814 and 815 are operated temporarily in circuits traceable through the back contacts of the relays of register 502 and thence to ground over conductor 518.

In the manner similar to that already explained the tens register relays 816 and 817 are operated in circuits traceable through the front contacts of relays 403 and 404 and relays 818 and 819 are operated in circuits through the back contacts of the remaining two relays of register 400, relay 822 is operated through the front contact of relay 408 and relays 820,- 821 and 823 are operated through back contacts of the remaining three relays of. register401, and relay 829 is 0 erated through the front contact of relay 409 and relays 826, 827 and 828 are operated in circuits through the back contacts of the remaining relays of the stations register 402.

When all of the register relays in the marker have operated, relay 809 is operated in a circuit from battery through its winding, thence through series contacts of all the relays in registers 804, 803, 802, 801 and 800 to ground. Relay 809 looks through its lower contact, normal-contact of relay 810 to the grounded conductor 811. Relay 809 operates the relay 810 in an obvious circuit. Relay 810 opens the locking circuit of relay 809 and closes a locking circuit for itself. Belay 809, inoperatin opens the circuits ays in the marker which do not correspond to the operated register relays in the sender, and these relays, thereupon, become released. Relay 809 becomes deenergized.

Connection of the marker to the incoming selector frame.

The frame connector 1000 is next operated to associate the marker with the group of incoming frames and also with the particular incoming selector frame 200 to which the calling line has been extended. For this purpose relay 1004 is operated in a circuit from battery through its winding, conductor 1007, inner right back contact of relay 805, right front contact of relay 806, conductor 826, upper contact of relay 810 to the grounded conductor 811. It will be noted that the relays 806 and 805 may be operated in different con 'binations to select other conductors similar to the conductor 1007 leading to other frame connectors (not shown). Relay 1004 operates the relay 1005 in a circuit traceable through the back contact of relay 1008, back contact of relay 1002 to ground at the back contact of relay 1003. lielay 1005 operates relay 1003 in a circuit from battery through the winding of relay 1003, right back contact of relay 1002,

" lower contact of, relay 1005, conductor 1009,

through outerri ht contact of relay 912' to the grounds "conductor 913.. slightly slow to release, does not retract its armatures while relay 1003 is operating. Relay 1003 closes a circuit from battery through the upper winding and contact of relay 1005, thence through the winding of relay 1002 to ground at the front contact of relay 1003. Relay 1002 operates and locks through its winding and front contact to the grounded conductor 1009. The circuit of relay 1003 is open when relay 1002 operates, but relay 1003, being slow to release, does not retract its armature until after relay 1002 has had time to close its front contact. The multi-contact relay 1006 is then operated in a circuit from battery through its winding, upper contact of relay 1005, left front contact of relay 1002 to ground at the back contact of relay 1003. The relay 1006 is individual to the marker shown and serves to connect the conductors from there to the grid wires of the frame connector 1000.

The next operation to take place is the ener ization of the vertical magnet 209 controlllng the vertical row of contacts 201 on the incoming selector switch 200 in which appears the trunk 110. A circuit for this purpose may be traced from grounded conductor 1009, contact of relay 1006, conductor 1011, normal contact of relay 914, conductor 915, thence over conductor 717, thence through the sender and sender selector switch 103, over one of the talking conductors through the district selector 109 to operate a relay in the trunk circuit 110 such as the relay 11.3. circuit is completed from the marker through the sender connector and thence the sender and sender selector switch is fully described in detail in the above-mentioned patent to S. B. Williams, No. 1,517 ,381, granted Dec. 2, 1924. The relay 113 applies ground potential to conductor 114 which extends through the winding of the magnet 209 to battery. The magnet 209' rotates the bar 207 and prepares the contacts in the vertical row 201. The multi-contact relay 1001 individual to the incoming selector 200 is also operated in a circuit from battery through the winding of said relay, conductor 1012 to ground through the contact of relay 113. Relay 1001 connects the grid wires of the frame connector 1000 to the leads extending to the incoming switch 200. Magnet 209 operates the relay 914 in a circuit from battery through the winding Relay 1005 being 7 The manner in which this r of said relay, conductor 916, through the the winding and contact of relay 1001,

Commotion of tile marker to translator.

The next step in the process is to associate the marker with the particular one of the five final translators which has control over the group of final switches reaching the group of 2000 lines containing the called line 318. The selection of the proper final translator is determined by the thousands digit which, it will be remembered, is re corded on the marker register 800. Therefore, when relay 1005 operates a circuit is closed for operating the relay 1108 which is individual to this particular marker at the connecting device 1100. This circuit may be traced from ground through the back contact of relay 1003, front contact of relay 1002, uppermost contact of relay 1005, conductor 1010, inner upper contact of relay 810, right front contact of relay 808, outer right back contact of relay 840, conductor 827, winding of relay 1108 to battery. Relay 1108 closes an operating circuit for relay 1105 including the contacts of relays 1106 and 1107. Relay 1105 operates the slowrelease relay 1107 in a circuit through the Winding of the latter relay, left contact of relay 1106, left contact of relay 1105, conductor 1110, right back contact of relay 911, thence through the grounded conductor 913. Relay 1105 being slightly slow to re lease, does not retract its armatures while relay 1107 is operating. Relay 1107 closes a locking circuit for relay 1105 and an operating circuit for relay 1106. Relay 1106 operates and locks through its left front contact, left contact of relay 1105 to ground over conductor 1110. Relay 1107 thereupon releases. The multi-contact relay 1103 is now operated in a circuit through its winding, contact of relay 1105, front contact of relay 1106 to ground at the back contact of relay 1107. Relay 1103 connects the various leads from the marker to the conductors extending to the final translator shown in Fig. 12.

The operation of the final translator will next be discussed. Inasmuch as the hundreds digit of the wanted line is 2, the hundreds relay 1211 is operated in a circuit from battery through its winding, conductor 1222, through the connector 1100, conductor 1111, inner right-hand contact of relay 812, inner right front contact of relay 813, inner right back contacts of relays 814 and 815 to the grounded conductor 826. Since the units digit is 4 and, consequently, less than 5, the relay 1218 is operated in a circuit from battery through the winding the final of said relay, thence through the connector 1100, conductor 1112 to ground at the back contact of relay 823.

Since the thousands digit is 2 and even the multi-contact relay 1208 is operated in a circuit from battery through the winding thereof, lowermost contact of relay 1211, inner contact of relay 1218, thence throu h the connector 1100, conductor 1113, rig it back contact of relay 84:2, inner upper contact of relay 810, to ground over the conductor 1010.

Due to the fact that the tens digit of the wanted number is 3, the relay 1209 is energlzed in a circuit from battery through the Winding thereof, through the connector 1100, conductor 1114, inner right front contacts of relays 816 and 817, inner right back contacts of relays 818 and 819 to the grounded conductor 826.

The translator has thus been operated and a selecting circuit is now completed therethrough for selecting and operating the vertical operating magnet 316 on the final selector 300 which controls the particular vertical row of contacts 303 in which appears the called subscribers line 318. The circuit for this purpose may be traced from ground, over conductor 826, thence over conductor 828, through the connector 1100, conductor 1223, lowermost contact of relay 1209, contact of relay 1208, conductor 1224, Winding of the magnet 316 to battery. Magnet 316 rotates the bar 320 and prepares all contacts in the vertical row 303. Magnet 316' also operates the relay 1204 which is individual to the final connector frame 300 and which serves to connect certain leads from the translator to said frame. The circuit for this purpose may be traced from battery through the winding of relay 1204, back contact of relay 1225, conductor 1226, inner contact of magnet 306 to ground over conductor 1224 as previously traced. Magnet 316 and relay 1204 lock in circuits from battery through the winding and inner contact of magnet 316, thence through the lower contact of said magnet and in parallel thereto from battery,through the winding of relay 1204 and thence over conductor 1226, through the lower contact of magnet 316 and thence over the conductor 321, con ductor 1227, conductor 908, right back contact of relay 907, outer right back contact of relay 906, outer left contact of relay 910, right back contact of relay 911, inner right contact ofrelay 912 to the grounded conductor 913.

Inasmuch as the units digit of the wanted line is 4 and the line appears in the section 311 of the connector switch 300, it will be necessary to operate the mnlti-contact relay 1206 of the connecting device 1201 in order to connect the testing leads from the marker to the horizontal links of the group 311 in eizclusion to other groups inthe connector switch. The circuit for relay 1206 may be traced from battery through its winding,

contact of relay 927, inner right back contact of relay 928, conductor 929, through 1100, conductor 1117, through the connector conductor 1228, through the connecting dethe rela 1015, conductor 1022 to the vice 1 100, conductor 1115, right front con-' grounde sleeve conductor of trunk 213. tact of relay 822, right back contacts of The link 305 also being busy, a circuit is relays 821 and 820 to the grounded conductor 826. Relay 1206 looks through its winding and contact to the grounded conductor 1227.

Connection of the marker to the group of trunks interconnecting the imam-mg a final switches.

Inasmuch as the incoming switches have groups of trunks leading to the final switches of the several terminal line groups, it is essential that the marker be connected to the particular group of trunks wh ch leads to the final selector 300 containing the called subscribers line. i

The identity of the incoming selector group may be had from the incoming frame connector 1000 and the identity of the group of final switches may be had from the translator connector 1100. Accordingly, the multi-contact relay 1015 is operated in a circuit from battery through its winding, contact of relay, 1016, conductor 1017, through the connector 1100, conductor 1116, through the frame connector 1000 and returning over conductor 908 to ground. 'Relay 1015 is individual to the group of trunks including the trunk 213 and serves to connect the marker testing equipment to the sleeve conductors of these trunks. Itelay 1015 operates the relay 1019.

Testing the trunks and links and called line.

with a series of a suflicient horizontal The marker is provided testing relays 920 comprising number of relays for testing the links of the incoming selectors, the trunks outgoing therefrom, and the horizontal links of the final selectors. The double- Wound relays 921, 922, 923, etc. each have a winding for testing a horizontal link in the incoming switch and a winding for testing the trunk which has access to such link. lilither winding is sutficient to operate the relay and both windings will also operate the relay. pertain to the corresponding horizontal links in the connector switch. Assume, first, that the link 205 of the first trunk 213 and the link 305 of the connector switch are all simultaneously busy. A circuit is, therefore, completed from battery through the left winding of tor of the link 205.

test relay 921, innermost back contact of relay 927, through the connector 1000, conductor 1020 to the grounded sleeve conduc- Another circuit is closed from battery through the right winding of relay 921, next to the inner back The relays 924, 925, etc.,

the incoming switch 200,

closed foropera'ting relay 924 which may be traced from battery through the outer left contact of relay 930, winding of relay 924, conductor 931, contacts of relay 1019. conductor 1023, through the connector 1100 conductor 1118, through the connecting device 1201, through the connecting device 1202, conductor 1229 to the grounded sleeve conductor of the link 305. Had the link 205 and the trunk 213 been idle the busy condition of link 305 would cause the o eration of relay 924, which in turn, wo d cause the operation of relay 921. The operating circuit for relay 921 in this case may be traced from battery through its right winding, inner contact of relay 924, outer right back contact of relay 930, conductor 932 to ground at the inner right contact of relay 900. The relay 921, in operating extends the start conductor 933 on to the next or may not be energized according -to the condition of the corresponding links and trunk.

If, however,- the first link 205, trunk 213 and the link 305 are all idle at the time, the test relay 921 remains deenergized. The magnet 212 which controls the yertical row of pear the trunks of the selected group is also operated at this time. The circuit for this purpose may be traced'from battery, through the winding of said magnet, conductor 215, through the connector 1000, conductor 1024, through the connector 1100, conductor 1119, contacts of relay 1015, con ductor 1230, contacts of relay 1206, contacts of relay 1204, conductor 1231, through the connector 1100, conductor 1120, contacts of relay 1019, conductor 1121 to the grounded conductor. 908.. The magnet 212 rotates the bar 216 and prepares the contacts in the vertical row 204. I

The magnet 212 operates the relay 930 in a circuit traceable from battery through the winding of said relay, contact of relay 903, conductor 934, contact of magnet 212 and returnin through the connector 1000 to groun over conductor 1009. Relay 930 opcrates the relays 927, 928 and 905. A circuit for this purpose may grounded conductor 932, through the outer right front contact of relay 930, thence in parallel through the winding relay 927 and through the inner right contact of relay 910, conductor 933, back contact of relay 935,1eft back contact of relay 921, winding of relay 928, winding of relay 905 to battery.

contacts 204 in which aptest relay 922 which may be traced from the Ill 1 of the called line 318. When switch in the contacts of also being made of the condition of the called subscribers line. At the time the connecting devices 1202 and 1201 are operated, the magnet 310 is energized in a circuit from battery through its winding, thence through contacts of connecting devices 1202 and 1201 to the grounded conductor 1227. Magnet 310 operates the common test link 307 which makes connection with the sleeve conductor relay 930 later operates, a test circuit is closed from battery through the winding of relay 911, front contact of relay 930, outer right back contact of relay 910, left contact of relay 936, conductor 937, contact of the connector 1100, conductor 1232, contact of relay 1204, conductor 322, over the test link 307 to the sleeve conductor of line 318. Assume the line 318 to be idle at the time relay 911 fails to operate.

With'the test relay 928 operated, as above explained, a circuit is closed for operating the vertical magnet 315 on the final selector which the trunk 213 appears. This circuit may be traced from the grounded conductor 908, thence through the outer right contact of relay 928, conductor 939, contacts of relay 1019, conductor 1025, through the connector 1100, conductor 1122, through the relay 1015, conductor 1233, through the relay 1204, winding of magnet 315 to battery. Magnet 315 rotates the bar 313 and prepares the contacts in the vertical row 301. The magnet 315 also causes the operation of the horizontal magnets 217 and 309 to complete the connection to the called line. The circuit for magnet 217 may be traced from battery to the right winding of said magnet, conductor 218, through the frame connector 1000, conductor 1026, outer left contact of relay 928, conductor 940, through the connector 1100, conductor 1123, through the connector 1202, contact of magnet 315, conductor 1226, contact of magnet 315 to ground over conductor 321. Magnet 217 operates, rotates the bar 220 and establishes connection between the trunk 110 and the trunk 213 through the medium of link The circuit for magnet 309 may be traced from battery, through the right winding thereof, conductor 323, through the connector 1202, through the connector 1201, thence through the connector 1100 to conductor 1124, thence through the relay 1019, conductor 1027, outer left contact of relay 928 and thence to ground over conductor 940 as traced. Magnet 309 rotates the bar 314 and the trunk 213 is connected to the line 318 through the medium of the idle link 305. en magnet 217 operates it closes the locking circuit for itself from battery through both windings thereof, thence through contacts of the switch 200 to the grounded sleeve conductor of the trunk 110.

When the switch 200 energized in a circuit from battery through its normal contacts, right windin of relay 324, sleeve conductor 327, through contacts of the switch 200 to the grounded sleeve conductor of trunk 110. Relay 324 operates and closes the holding circuit from battery through the winding of relay 325, right front contact of relay 324 to the grounded conductor 327. Relay 325 also operates in this circuit and applies ground potential to the sleeve conductor 328. When magnet 309 olperates it looks through both its windings to t e grounded conductor 328.

In any suitable manner, ringing current may be applied to ring the subscribers bell whereafter the parties may hold conversation over the established connection.

Release of the sender and marker.

At the time the test is made of the links and trunks a circuit is completed for initiating the restoration of the sender. This circult may be traced from the grounded conductor 908, thence through the outer right contact of relay 905, conductor 941, thence through the sender connector 700 to the reg ister sender 107. The closure of this circuit may serve to operate a relay in the sender to bring about disconnection of the sender from the marker in the manner explained in the patent to S. B. Williams N 0. 1,517,331, granted Dec. 2, 1924. Relays 701 and 702, in releasing, due to the disconnection of the sender, cause the release of relay 703. Relay 705, however, remains energized in a circuit through its upper winding, thence over conductor 718 to the grounded conductor 913.

At the time ground is applied to conductor 328 a circuit is completed for operating the marker release relay 903. his circuit may be traced from battery, through the winding of said relay, inner right front contact of relay 928, conductor 929, thence as previously traced to conductor 1022, thence to a grounded conductor 328. Relay 903 rcleases relays 900 and 930 and these relays, in turn, remove ground from the various holding conductors to permit the restoration of the marker and associated equipment.

OaZZed subserz'bers Zine tests busy.

In case the called line is busy at the time the test is made, the busy test relay 911 is operated in the circuit heretofore traced. Relay 911 at its right contact causes the release of the operated test relays 920, the marker connector. 1100, the relays 1019 and 1015, connector 1202, the line vertical magnet 316, test horizontal magnet 310 and the vertical magnet 212. The connection originally started is thus wi ed out when the called subscribers line is ibuud to be busy.

en magnet 212 releases, it causes the release of relay 930 which, in turn, releases operates relay 324 is 

